Mixed olefinic/aromatic tackifier resins have been prepared from a wide variety of feedstocks including
(a) Cut piperylene (piperylene concentrate) of which 1,3-pentadiene is a main component and C.sub.5 olefins are a minor component. PA1 (b) Steam cracker olefins: mainly composed of Pentene-2,2-methyl-butenes 1,2 and cyclopentene. Steam cracker olefins is predominantly mono-olefinic. PA1 (c) Heart cut distillate containing vinyltoluenes and indene as main components but also containing styrenics such as styrene and alpha-methylstyrene. Some styrenics have a lowering effect on softening point. PA1 (d) Other aromatics (especially Indenics) tend to increase softening point. PA1 (e) Cyclopentadiene and dicyclopentadiene which have a broadening effect on molecular weight distribution and tend to increase the softening point. PA1 (1) preparing a resin from a feed containing a piperylene stream and an olefinic stream to provide a diolefin/olefin ratio (D/O) of from 1/10 to 1/1 and a heart cut distillate stream containing C.sub.8 to C.sub.10 aromatics to provide at least 5 wt % of indenic feed material using Friedel-Crafts catalyst to provide a resin having an aromaticity in the resin of at least 25%, preferably at least 30% in equivalent wt % styrene; and
Specific disclosures include:
Tack/fiefs for SBS with relatively low molecular weights prepared by using a Friedel-Crafts catalyst and polymensing a mixture of C.sub.5/ C.sub.6 (di)olefins and C.sub.8 /C.sub.10 aromatics are disclosed in U.S. Pat. No. 4,078,132 (Lepert) and EP-A-23456 (Evans). The softening points are low in EP-A-23456 (Evans).
In Lepert Example 12 molecular weights and aromaticity are high. However the material does not tackify SBS satisfactorily. Ball tack is 4 to 30 cm and so is too high.
In Evans such high amounts of chain transfer agent (mono-olefins) are used that the softening point is very low. The product will not provide a good adhesive/cohesive performance in SBS blends. The liquid resin serves to substitute the oil in hot melt adhesive (HMA) but cohesive performance is reduced. U.S. Pat. No. 3,784,530 (Goodyear) describes a hydrocarbon resin tackifier having a softening point of from 60.degree. to 110.degree. C. prepared by polymerizing piperylene, 2-methyl-2-butene, dicyclopentadiene and alpha-methyl styrene. The polymerization uses Friedel-Crafts catalyst systems. At least 15% of 2-methyl-2-butene is used in the feed stream which also contains appreciable amounts of piperylene and dicyclopentadiene components and an aromatic component in the form of the alpha-methyl styrene.
The resulting resin is not hydrogenated. It is said to be suitable for track/lying natural and synthetic rubbers including butadiene-styrene copolymers. There is no specific disclosure of block-copolymers. The amounts of 2-methyl-2-butene used are high (above 15 wt %) and this adds to the cost of the resin. At least 15 wt % must also be used of a costly alpha-methylstyrene component to provide the desired aromaticity. The amounts of aromatic component added are minor but the feed components have to be fairly pure (hence the use of alpha-methylstyrene) if a low Gardner colour, rubber-compatible tackifier resin is to be obtained.
U.S. Pat. No. 3,846,352 is a divisional application from U.S. Pat. No. 3,784,530 with almost identical disclosure. U.S. Pat. No. 4,037,016 discloses a resin prepared by Friedel-Crafts polymerisation which is used in an adhesive composition including block copolymers,-with end-blocks forming from 10 to 50 wt % of the copolymer. The tackifying resin has carbon to carbon unsaturation and therefore must be essentially non-hydrogenated. The softening point is low from 60.degree. C. to 80.degree. C.
The feed stream appears to have a similar composition to that described previously but uses higher levels of costly alpha-methyl styrene (over 40 wt %). Other branched chain mono-olefins are described other than 2-methyl-2-butene although 2-methyl-2-butene still seems preferred.
U.S. Pat. No. 4,046,838 describes a block copolymer blend with a resin. The block copolymer may be an SBS. The resin has a softening point of a range of 60 to 110.degree. C. The composition of the resin feed stream appears identical to that of earlier Goodyear documents referred to. The adhesive compositions may be used as a pressure sensitive adhesive.
U.S. Pat. No. 4,104,327 discloses an adhesive composition comprising a block copolymer (including SBS) and a hydrocarbon resin. The hydrocarbon resin contains from 40 to 95% by weight of a C.sub.5 1,3-pentadiene (piperylene) component and from 60 to 5% by weight of an alpha-methyl-styrene unit in the polymer chain.
In the examples 1,3-pentadiene is used exclusively as a diolefin component with much smaller amounts of alpha-methyl-styrene. Table 1 summarizes the examples. No comparison is made with a resin containing C.sub.5 diolefin and C.sub.5 olefin including branched chain mono-olefins and major amounts of an aromatic component.
Relatively costly pure feedstocks are used. The molecular weight distribution is not given.
EP 175,593 (Exxon) uses a hydrocarbon resin derived from a C.sub.5 C.sub.6 olefin and diolefin feed as well as from 5 to 30 wt % of para-methyl styrene. The use of para-methyl styrene as opposed to alpha-methyl styrene prevents the decreasing of the softening point. By far the larger amount is olefin and diolefin. The olefinic feed stock is a mixed stream obtained by the cracking and distillation with from 50 to 14.5 wt % of diolefin, from 33.5 to 13 wt % of olefin and from 20 to 35 wt % of aromatics. The stream contains from 4.5 to 15.5% of 1,3-pentadiene. It is suggested that cyclopentadiene levels have to De kept low. It is suggested on page 7 that optionally transfer agents may be used such as branched chain aliphatic olefins as disclosed in GB 1538 057 to narrow the molecular weight distribution. A wide variety of end-uses is suggested. In the examples, no specific transfer agent appears to be used. Aromatic levels in the resulting resin are not described.
U.S. Pat. No. 4,952,639 (Maruzen) discloses a resin and hydrogenation step. Adhesive compositions with ethylene-vinylacetate copolymers are prepared. The precursor resin is prepared using C.sub.5 diolefins (D), C.sub.5 monoolefins (O) and aromatic monoolefins where the D/O ratio is from 1/1 to 4/1. The resin is hydrogenated extensively. This leads to saturation of at least 80% of the unsaturated bonds of the olefin components and also at least 80% of the aromatic component which is present in an amount of at least 10 wt %. Branched chain olefins are not specifically added although they may be part of an olefinic or a diolefinic feed stream and may indeed be present in a high concentration (13-23 wt %) See Table 8. Both pure styrenic streams and mixed streams are proposed as aromatic components.
WO 9107472 (Exxon) (PCT/GB/001749) discloses an adhesive formulation for blending with SBS to make an adhesive formulation including from 40 to 90 wt % of C.sub.5 olefins and diolefins and from 10 to 50 wt % of a C.sub.8 -C.sub.10 aromatic component to give an aromaticity of from 13 to 45 wt % and an Mw/Mn of less than 1.7.
It is therefore an object of the invention to provide a hydrocarbon resin which can be hydrogenated to provide a low-colour styrenic block copolymer compatible resin and a process for making such resin from mixed, low cost feed streams.
It is a further object of this invention to provide an adhesive composition containing a block copolymer, particularly one having high levels of styrene block elements, which provides good adhesion characteristics and which in particular is homogeneous and has a low zippiness, that is to say can be pulled away from a substrate under a constant force without jerking.